The objectives of this Phase III clinical research study are: 1) To determine the effect of orlistat plus diet compared to placebo plus diet on weight loss over 52 weeks in obese Type 2 diabetic patients treated with metformin monotherapy. 2) To determine the effect of orlistat pluse diet compared to placebo plus diet on glycemic control form baseline to week 52 as determined by HbA1c in obese Type 2 diabetic patients patients who are maintained on a stable dose of metformin.